Signficance The immunogenicity of two hybrid sperm ADAM peptides in cynomolgus macaques were evaluated to determine whether the antibodies produced bind to homologous spermatozoa and therefore could be used as a contraceptive vaccine. Objectives Antibody titers obtained through four intramuscular (IM) injections of the two antigens were evaluated. Briefly, two treatment groups consisting of 3 and 2 animals respectively were placed into groups 1 and 2. Group 1 received antigen 1, sperm surface protein fertilin b (long form) in tandem with T cell epitope from malaria circumsporozooite and group 2 received antigen 2, sperm surface protein cyrestin in tandem with the same T cell epitope. The adjuvant used for both antigens was MPL-SE (Ribi). The dosing concentration for the primary treatment was 300 5g/0.21 ml for each animal in the study. The three booster injections were 100 5g/0.21 ml per animal. Animals received their primary treatment on study day 0, with booster injections taking place on study days 14, 28 and 77 respectively. Blood was collected once prior to primary treatment, then on days 14, 28 and 42 of the study. After study day 42, blood collections continued once per month. Vaginal wash and cervical mucus samples will be collected at times to be determined excluding menses. Results All blood samples were processed for serum, then forwarded to Dr. Cherrie Brown for antibody titer assessment. Serum was assayed by ELISA, for titers of antibodies against each of the peptides. Isotypes (IgG vs. IgA) were also determined. Future Directions Depending on the results obtained, future studies could include a fertility trial to assess contraceptivity. KEYWORDS immuno-contraception, sperm antigens, vaccine